The following Technical Specifications are incorporated herein by reference:
“3GPP TS 25.214 V7.7.0 (2007-11)”, also known as “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical layer procedures (FDD) (Release 7)” (referred to herein as “TS 25.214”); and
“3GPP TS 25.212 V7.7.0 (2007-11)”, also known as “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Multiplexing and channel coding (FDD) (Release 7)”.
The document TS 25.214 specifies “HS-SCCH-less” (also referred to as “HSL”) operation that targets low throughput applications that utilize HSDPA (High Speed Downlink Packet Access). Examples of applications include Voice over IP (VoIP) communication, and interactive gaming. The HS-SCCH-less feature aims to increase cell capacity in HSDPA operation by reducing signalling overhead normally associated with the control channel known as HS-SCCH (High Speed Shared Control Channel). As its name implies, the HS-SCCH-less feature supports HSDPA operation without the control signalling overhead associated with the use of HS-SCCH.
Normally in HSDPA operation, each downlink data transmission on HS-DSCH is preceded by a corresponding downlink transmission of control information on HS-SCCH. This control information specifies how the UE (user equipment, for example, a cell phone) is to decode the corresponding data transmission. It normally identifies an HS-DSCH transport format. An HS-DSCH transport format (TF) specifies the following parameters: transport block size (physical layer packet size); set of OVSF (Orthogonal Variable Spreading Factor) codes associated with HS-PDSCH (High Speed Physical Downlink Shared Channel); and modulation (e.g., QPSK).
The HSL mode of operation provides for up to three attempts at the physical layer to transmit a given data transport block on the downlink data channel known as HS-DSCH (High Speed Downlink Shared Channel). If a first transmission attempt is unsuccessful, as evidenced by the absence of an expected acknowledgement (ACK) on the uplink from the UE, then a second transmission attempt (i.e., a first retransmission) occurs. If the second transmission attempt is unsuccessful, as evidenced by the absence of an ACK or the presence of a NACK (negative acknowledgment) on the uplink from the UE, then a third transmission attempt (i.e., a second retransmission) occurs. In HSL mode, a given data transmission on HS-DSCH is characterized by any one of (up to) four possible transport formats (TFs).
According to HSL operation, HS-SCCH is not used to transmit control information associated with the first downlink data transmission attempt for a given data transport block. The UE is thus required to decode the data transmission without any control information that specifies how the decoding should be done. This decoding of a data transmission without benefit of associated control information is referred to as blind decoding. For blind decoding of the first downlink data transmission attempt, the UE assumes a given transport format, and performs derate matching (i.e., de-puncturing or de-repeating of bits in the received transport block) according to a redundancy version (RV) that TS 25.214 specifies for the first downlink data transmission attempt. The UE attempts to blind decode the first downlink data transmission using the RV that TS 25.214 specifies for the first downlink data transmission attempt, and up to four (if necessary) transport formats. The document TS 25.214 indicates that the UE will apply this same blind decoding procedure with respect to any downlink data transmission attempt for which no corresponding HS-SCCH control information can be decoded.
It is desirable to provide for improving the success rate of blind decoding at the user equipment.